Process for treating oils



Dec. 2l, 1943. D, E. CARR PROCESS FOR TREATING OILS Filed Jan. 24, 1940 IIIY Sw* Patented Dec. 21, 1.943

NT OFFICE PROCESS FOR TREATING OILS Donald E. Carr. Los Angeles, Calif., assigner to Union Oil Company of California,

LOS AD.-

geles, Calif., a corporation of California Application 'January 24, 1940, Serial No. 315,348

8 Claims.

-This invention relates to a process for separating sulfur from oils. The invention relates particularly to a process for desulfurizingl high sulfur residua obtained from sulfur' bearing crude oils preparatory to subjecting the residua to coking operations to obtain coking distillates.

In recent years, considerable attention has been directed by the petroleum refiners to the conversion of high asphalt content crude oil residue to obtain motor fuels of the gasoline type.

One of the methods employed for obtaining motor fuels or distillates which may be converted by cracking into motor fuels is the socalled :coking distillation method which consists essentially in subjecting .the heavy petroleum residuum to suiiicient heat as is necessary to remove substantially all of the vaporizable oil constituents from the residuum leaving a solid dry coke as an undistilled bottoms. I However, the residues primarily used for coking operations often contain fractions of high sulfur content which vaporize with the distillates during coking and are thus retained in the distillates. This, of course, results in a 10W grade motor fuel which must be treated to remove the sulfur to produce an acceptable motor fuel.

Experimentation has indicated that high sulfur residuum, such as that obtained from Santa Maria Valley crude pil, may be treatedl at relatively low non-coking temperatures to remove a considerable amount lof sulfur in the form of hydrogen sulfide. Further study of this phenomenon under closely controlled conditions has shown that the loss of sulfur occurs almost entirely in the asphaltene fraction of the residuum. Under properly chosen temperature conditions, the amount Aof this fraction is' not substantially. changed and little coke is formed,y but the sulfur content can be reduced considerably; whereas, the sulfur content of the oil fraction re/ On the other mains substantially constant.

hand, if conditions are selected which also resultl in the desulfurization of the oil fraction, the -asphaltene fraction is found to Ycoke badly.

I have discovered that the sulfur content of a very heavy high sulfur residuum may be considerably reduced by a selective thermal treatment of the residuum in analogy with the Selective multiple coil cracking of crudes or reduced crudes wherein the crude or reduced crude is typically separated by distillation of such fractions as gasoline which may, if desired, be 'put through a high temperature reforming coil, as gas oil, which may be put through a medium temperature cracking coil and as fuel oil residuum, which may be put through a low temperature viscosity reducing coil. As a matter of fact, the asphaltenes and oils present in heavy residuum are often more divergent in molecular weight and thermal stabilityhthan gasoline, gas oil and residuum fractions employed in the usual cracking process and therefore would require even more selective conditions to give optimum results. l

In order to accomplish such a selective pyrolysis with heavy residues consisting of asphaltenes, resins and heavy lubricating oils, I subject the heavy residue to a preliminary separation of these constituents by means of solvent capable of dissolving the heavy lubricating oils and resins leaving the asphaltenes as an undissolved fraction. Preferably, the separation of the heavy residue by means of the solvent is carried out under such conditions as to produce an undissolved asphaltene fraction of about 350 F. melting point and a resinous oil which is liquid at room temperature. The asphaltene fraction is next subjected, either with or Without prior removal of the solvent associated with this fraction, to cracking under controlled temperature conditions, preferably at about 675 F. for a rather extended soaking period. 'I'he main function of this pyrolysis is to eliminate a large portion of the sulfur in the asphaltenes as hydrogen sulfide which is separated along with other permanent gases from condensable distillates by appropriate methods. The partly desulfurized bottoms may then be subjected to coking, if desired, after 'adding the extracted oil fraction to these bottoms thus obtaining coking distillates of much lower sulfur content than would have been obtained Without preliminary low temperature pyrolysis. Any of the coking methods now known or employed may be used. I prefer that the socalled delayed method consisting in passing the 'bottoms through a, heating coil into a coking chamber, the heat input to the asphaltenes in the heating coil being sufficient to eifect the coking WhenA the heated asphaltenes are passed into the coking chamber. i

Instead of adding the extracted oil fractions directly to the asphaltene fraction which is subjected to desulfurization, the extracted oil fraction may be separately treated 'by any of the well known desulfurization methods such as, for example, treatment with sulfuric acid, Edeleanu treatment with liquid sulfur dioxide, phenol treatment, etc. The thus partly desulfurized oil may then be blended with the partlydesulfurized may be cycled to the asphaltene fraction pass.

ing to the desulfurization operation or if desired, the entire heavy oil fraction producedv from the cracking operation to produce the gasoline may be recycled to the oil undergoing extraction in which case the oil contained in the heavy oil fraction will be recycled together with the extracted oil'from the fresh charge to the cracking operation and the asphaltene fraction contained in the heavy oil fraction will be recycled together with the asphaltene fraction from the fresh charge to the desulfurization and coking stages. y

In order to effect the separation of the heavy residuum into asphaltenes and heavy resinous lubricating oil, the heavy residuum ismixed with an appropriate quantity of solvent such as, for example, one to six volumes of liquid butane at a temperature of about 150 F. under a pressure of 125 lbs. per square inch and the mixture is allowed to stratify into two layers, i. e. an` upper layer of the resinous oil dissolved in the solvent and a lower layer of the asphaltenes containing some oil and solvent. The upper layer is decanted from th'e asphaltene layer and each layer may then be heated to ak temperature sufficient to distill the solvent contained therewith.

As solvents adapted to separate the heavy residuum. into the aforementioned asphaltene and resinous lubricating oil fractions, I prefer to use a liquefied normally gaseous hydrocarbon, such as ethane, ethylene, propane, propylene, butane, butylene and iso-butane or mixtures thereof. Butane is a preferred solvent for this purpose. However, I may employ such other solvents as pentane, hexane, gasoline, naphtha, alcohol, ether, mixtures of alcohol and ether, acetone and -other solvents capable of. dissolving the oil and resins but not the asphaltenes. It will be understood that the amount of solvent employed and the operating temperature and pressure conditions mustbe controlled to suit the particular solvent and the stock being treated in order that a proper solution of only the resinous oil con stituents is obtained.

It is thus an object of my invention to remove sulfur from heavy asphaltic oils. It is a speciiic object of my invention to remove sulfur from the asphaltene fraction of the heavy asphaltic oil by pyrolysis.

Another object of my invention resides irr separating the heavy asphaltic oil into an asphaltene fraction and a resinous oil fraction and separately desulfurizing the asphaltene fraction by pyrolysis. Another. object is to subject the desulfurized asphaltene fraction to a coking operation preferably after adding thereto the separated resinous oil fraction. A specific object of the invention is to effect the separation of the oily fraction from the asphaltene fraction by means of a solvent.

, Other objects, features and advantages of my invention will be ,apparent from the following description of my invention taken from the drawing which represents a schematic arrangement of apparatus for carrying out a preferred embodiment of my invention. v

Referring to the drawing, a heavy road oil of asphalt produced by distilling a sulfur-containing asphalt base crude oil to separate gasoline, kerosene, gas oil to leave a residue consisting of asphaltenes, resins and heavy lubricating oils is taken from storage tank I via line 2 controlled byvalve 3 and is pumped by pump 4 into line 5. A light hydrocarbon solvent such as butane is taken from tank 1 via line 8 controlled by valve l9 and pumped by pump I0 through line I I into line 5. The amount of butane introduced into line 5 will depend upon the 'characteristics of the oil and the degree to which it is topped. Generally, however, from one to six volumes of the butane is mixed with the oil. The mixture then passes through mixing or turbulence coil I2 into asphalt separator I4 where sufficient time is provided to permit a heavy or hard asphalt to settle or stratify from the solution of oil and butane. The supernatant solution of oil and butane is withdrawn from the top of the asphalt separator via line I5 and passed through heater I6 where the oil is heated to a suiciently elevated temperature to vaporize the butane when passed into the evaporator I8 via line I1. In evaporator I8, the butane is vaporized from the oil and is withdrawn via line I9 controlled by valve 20. Additional heat may be provided in evaporator I8 by circulating lsteam through closed coil 2I. The debutanized oil at the bottom of the evaporator I8 is withdrawn via line 22 controlled by valv'e 23 and is pumped into line 25 by pump 24.

The asphalt settling at the bottom of the asphalt separator I4 iswithdrawn via line 26 controlled by Valve 21 and is pumped by pump 28 through line 29 and heater 30 where it is heated to a sufliciently high temperature to melt the asphalt and vaporize residual butane when passed into evaporator 3|. Vaporization of butane in evaporator 3| is aided by superheated steam circulated through closed coil 32. The overhead from evaporator 3| is withdrawn via line-33 controlled by valve 34. ,This overhead may be combined with the overhead from evaporator I8 which may then be compressed under pressure suicient to liquefy the butane, cooled and returned to butane storage tank 1.

The de-butanized asphalt at the bottom of the evaporator 3l is withdrawn via line 35 controlled by valve 36 and is pumped by means of pump 31 through heater 38 where the asphalt is heated to a temperature of about '100 F. and is passed via line 39 into the soaking chamber 40 where the asphalt is subjected to cracking under controlled temperature conditions, the temperature preferably being held to 670 F. fora rather extended soaking period. In chamber 40, the pyrolytic action resultsv in the removal of sulphur in ,the form of hydrogen sulphide from the asphaltenes as explained above. The hydrogen sulphide is removed via line 4I controlled by valve 42. Part of the necessary heat input during this soaking period may be conveniently provided by the introduction of hot gases via line 43 controlled by Valve 44.- If desired, hot volatile fractions from the pyrolysis of the oil fraction described hereafter or from similar volatile frac- Y in the soaking chamber 40.

tions of simultaneous gas-oil cracking or reforming processes may be introduced into the asphalt I The introduction of such gases under the surface of the asphalt serves also to agitate the material and facilitate the evaporation of any distillable fractions formed drogen sulphide.

during the pyrolysis of the asphalt. If desired, the gases issuing from the soaking chamber via line 4I may be subjected to absorption to remove the hydrogen sulphide and the remaining gases containing condensable hydrocarbons may be subjected to condensation to recover any oil fractions present in the gases.

The desulphurized asphalt may be withdrawn via line 45 controlled by valve 46 and pumped by pump ,41 through line 48vinto line 25 where it combines with the oil from evaporator 1 8. The blend of asphalt and oil is then heated in heater 49 to a coking temperature of approximately 900 F. and is passed via line 50 into the coking chamber where the oil is subjected to coking by any of the well known coking methods.

The coking distillates produced in the coking chamber are withdrawn via line 52 controlled by Valve 53 and subjected to fractionation in fractioning column 54, gasoline vapors and light gases being removed from the` column via line 55 controlled by valve 56, condensed in condenser 51 and passed via line 58 into separator 59 where uncondensed gases are withdrawn via line 60 controlled by valve 6|. Gasoline is withdrawn via line 62 controlled by va1ve63. Heavier oil fractions may be recycled to line 25 by pump 66 via line 64 controlled by valve 65. Alsoa light gas oil fraction suitable for cracking may be withdrawn from the side of the column via line 61 controlled by valve 6B and may be passed to suitable cracking apparatus not shown. If desired, this fraction may also be recycled to line 25 and passed through the heater 49 into the coking chamber 5i where it is subjected to further conversion into lighter fractions.

The coke formed in chamber 5I may be removed by any of the Well known means and withdrawn from the chamber via line 69 controlled by valve and pump ll.

In the foregoing description of the invention as taken from the drawing, the oil phase or the asphalt phase or both phases removed from the asphalt separator i4 may be passed directly through the heaters 38 and 49 and these fractions may thus be heated in the presence pf the butane instead of first stripping the butane from Vthese phases. The presence of these light gases 1 during the soaking or coking operations inhibits the formation of like gases from the oil fractions being subjected to the elevated temperatures under pressure.

The following is a specic example of one embodimentof my invention: A California crude oil obtained from Santa Maria Valley having a sulphur content of approximately 4.5% was distilled to remove gasoline, kerosene, gas oil, to produce a heavy residue of road oil consistency and having a melting point of approximately 110 F. The asphalt residue had a sulphur content of approximately 5.5%. Approximately six volumes of liquid butane under pressure. was

mixed with a portion of the asphalt residue at a temperature of 150 F. and the mixture was allowed to stratify into two layers. The lower layer consisted of a hard asphalt of about 350 F'. melting point. This fraction was then heated to remove the liquid butane contained in it andv was then subjected to cracking under controlled conditions maintaining a temperature of 675 F. for approximately three hours to remove hy- The upper phase' from the ashalt separator consisting of butane and resinous lubricating oil was stripped of butane and was then blended with the desulphurized asz5 phalt. A test on the blend now showed appro mately 3.8% of sulphur. This blend was then heated to approximately 900 F. and passed into a coking chamber to obtain a coking distillate 5 having approximately 2.9% of sulphur..

In another run, a portion of the heavy road oil containing the 5.5% of sulphur was subjected directly to the aforementioned coking operation to produce a coking distillate. This coking distillate contained approximately 3.9% of sulphur.

'I'he foregoing description of my invention is not to be `taken as limiting my invention but merely as illustrative of one mode of carrying it out as many variations may be made thereon as will be recognized by those skilled in the art which are Within the scope of the following claims.

1. A process for separating sulfur from sulfurbearing asphaltic oils which comprises separating said asphaltic oil into anasphaltene fraction and an oil fraction' and heating said asphaltenefraction in the absence of added hydrogen at a temperature of approximately 675 F. for a sufficient period of time to separate sulfur in the form of hydrogen sulde.

2. 'A process for separating sulfur from sulfurbearing asphaltic oils which comprises commingling said asphaltic oil with a solvent in' which the asphaltene fraction contained in said asphaltic oil is insoluble in said solvent but in which the oil fraction contained in said asphaltic oil is soluble, separating a solution of oil and solvent from an undissolved asphaltene fraction and heating said asphaltene fraction in the absence of added hydrogen at a temperature of approximately 675 F. for a sufcient period off time to separate sulfur in the form' of hydrogen o Sulde.

3. A process as in claim 2 in which the solvent comprises a liquefied normally gaseous hydrocarbon.

4. A process as in claim 2 in which the solvent comprises liquid butane.

fur bearing asphaltic oils which comprises separating said asph-altic oil into an asphaltene fraction and an oil fraction, heating said asphaltene to separate sulfur in the form of hydrogen sulde, blending said heated asphaltene fraction with said separated oil fraction and subjecting said blend of asphaltene and oil fractions to coking distillation.

6. A process for the coking distillation of sulfur bearing asphaltic oil which comprises comminglling said asphaltic oil with a. solvent in which the asphaltene fraction contained in said asphaltic oil is insoluble but in which'the oil fraction contained in said asphaltic oilis soluble, separating a solution of oil and solvent from an undissolved asphaltic fraction, heating said asphaltene fraction at a temperature suilciently elevated toseparate sulfur in the form of hydrogen sulfide, blending 7said heated `asphaltene i -fraction with said separated oil fraction and subjecting said blend of asphaltene and oil fractions to coking distillation.

7. A process for the coking distillation of sulfur bearing asphaltic oils which comprises separating said asphaltic oil into an asphaltene fraction and an oil fraction, separately separating sulfur from said asphaltene and oil gfractions, blending said treated asphaltene and voil frac- 5. A process for the coking distillation of sulfraction at a temperature sufficiently elevated tions and subjecting said blend of asphaltene and oil fraction to coking distillation.

8. A process for the coking distillation of sulfur bearing asphaltic oils which comprises separating said asphaltic oil into an asphaltene fraction and an oil fraction, separately heating said asphalterie fraction at a temperature sumciently elevated to separate sulfur in the form DONALD E. CARR. l 

